A user of a computing system, entering a query into a search engine, wants to receive query results that are relevant to the user. Whether the results returned by the search engine are relevant to the particular user entering the query is a subjective view of the particular user entering the query. Therefore, the more information that the search engine can gather about the particular user, the more likely it is that the search engine will return results that are relevant to the particular user. However, gathering information about particulars users raises privacy concerns.